A research letter published last week in JAMA asserts that teens who used e-cigarettes became “heavy” smokers. The research appears to have been engineered to produce that result.
The lead author is Adam Leventhal, a University of Southern California psychologist with a history of exaggerated anti-e-cigarette claims (here). Promoting his new research, Leventhal told the media (here) his work “…is the first to show that teenagers who vape not only experiment with cigarettes, but are also more likely to become regular smokers…It is also the first time teenage vaping has been linked to heavier smoking patterns involving use of multiple cigarettes per day.”
Leventhal conducted repeat surveys of Los Angeles-area high schoolers. A baseline survey of 10th graders was followed six months later by a second. Critical to the outcome, Leventhal defined vapers and smokers differently, as seen in this table.
|Leventhal’s Definitions and Classification of Baseline Vapers and Smokers|
|Past 30 days||Current vaper||Current smoker|
|Infrequent||1-2 days||1-2 days|
|Frequent||3+ days||3+ days|
Why did Leventhal use different definitions for vapers and smokers? Why did he separate past and never vaping, but combine past and never smoking? One possible explanation is that he wanted to record more “non-smokers” at baseline, some, perhaps many of whom, were “prior” smokers. This allowed Leventhal to count prior smokers as vaping gateway cases to subsequent smoking.
There are additional problems. Leventhal labeled those smoking on three or more days in the past month as “frequent,” and those consuming two or more cigarettes on days they smoked as “heavy” smokers. He provided no reference for these cutoffs, which help support his vaping-leads-to-smoking screed.
For context, note that the 2014 National Youth Tobacco Survey showed that nearly half of current 10th grade smokers smoked five or fewer days in the past month, and smoked five or fewer cigarettes (on days they smoked). These were likely weekend party smokers. Labeling infrequent users as “frequent” or “heavy” is inappropriate.
Leventhal’s study was supported by NIH grants to him ($3.4 million over five years) and Jonathan Samet ($15.9 million over four years).
The number of engineered e-cigarette gateway studies is growing, and they will have a major impact on FDA regulations. Federal grant support requires the authors to share their data (here). With the stakes so high, independent investigators who aren’t biased against e-cigarettes will eventually obtain Leventhal’s data, and his analysis, results and interpretation will surely be investigated.